The axial pin tumbler locks, also known as tubular locks or “Ace” locks, were invented in last century and have been developed for many years. The following U.S. patents are believed to represent the prior and current state of the art:                U.S. Pat. Nos. 4,112,820; 4,621,510, 4,802,354; 5,018,376; 5,400,629; 5,544,512; 6,357,271 and 7,150,168.        
As evidenced by these patents, a tubular lock generally includes a shell containing a plurality of first pin bores; a plug, rotatable within the shell, containing a plurality of second pin bores facing to the first pin bores on the shell; and a plurality of pin sets, each comprising a spring-loaded first pin and a second pin, in the prior state of the art. The locking mechanism is created by having each spring-loaded first pin that seated in the first pin bore on the shell extended into a corresponding second pin bore in the plug at their initial position so to span both the shell and the plug and block the plug from rotating. The second pins reside in the second pin bores in the plug for receiving and transferring external force and in turn moving their corresponding first pins away by a pre-determined distance from their initial position so to catch the shear plane between the shell and the plug. All second pins normally expose directly to the keyway with relatively bigger profile so that they are relatively easier to be accessed and manipulated by picking or bumping tools.
So far as we know, all the development tried to provide a relatively higher level of security within the prior state of the art of axial pin tumbler locking mechanism have not changed the core nature of double-pin-single-spring configuration. So the basic disadvantage of easily being picked open is not improved practically.